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+/*
+ * yosys -- Yosys Open SYnthesis Suite
+ *
+ * Copyright (C) 2018 whitequark <whitequark@whitequark.org>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ */
+
+#include "kernel/yosys.h"
+#include "kernel/sigtools.h"
+#include "kernel/modtools.h"
+
+USING_YOSYS_NAMESPACE
+PRIVATE_NAMESPACE_BEGIN
+
+struct OptLutWorker
+{
+ dict<IdString, dict<int, IdString>> &dlogic;
+ RTLIL::Module *module;
+ ModIndex index;
+ SigMap sigmap;
+
+ pool<RTLIL::Cell*> luts;
+ dict<RTLIL::Cell*, int> luts_arity;
+ dict<RTLIL::Cell*, pool<RTLIL::Cell*>> luts_dlogics;
+ dict<RTLIL::Cell*, pool<int>> luts_dlogic_inputs;
+
+ int eliminated_count = 0, combined_count = 0;
+
+ bool evaluate_lut(RTLIL::Cell *lut, dict<SigBit, bool> inputs)
+ {
+ SigSpec lut_input = sigmap(lut->getPort("\\A"));
+ int lut_width = lut->getParam("\\WIDTH").as_int();
+ Const lut_table = lut->getParam("\\LUT");
+ int lut_index = 0;
+
+ for (int i = 0; i < lut_width; i++)
+ {
+ SigBit input = sigmap(lut_input[i]);
+ if (inputs.count(input))
+ {
+ lut_index |= inputs[input] << i;
+ }
+ else
+ {
+ lut_index |= SigSpec(lut_input[i]).as_bool() << i;
+ }
+ }
+
+ return lut_table.extract(lut_index).as_bool();
+ }
+
+ void show_stats_by_arity()
+ {
+ dict<int, int> arity_counts;
+ dict<IdString, int> dlogic_counts;
+ int max_arity = 0;
+
+ for (auto lut_arity : luts_arity)
+ {
+ max_arity = max(max_arity, lut_arity.second);
+ arity_counts[lut_arity.second]++;
+ }
+
+ for (auto &lut_dlogics : luts_dlogics)
+ {
+ for (auto &lut_dlogic : lut_dlogics.second)
+ {
+ dlogic_counts[lut_dlogic->type]++;
+ }
+ }
+
+ log("Number of LUTs: %8zu\n", luts.size());
+ for (int arity = 1; arity <= max_arity; arity++)
+ {
+ if (arity_counts[arity])
+ log(" %d-LUT %16d\n", arity, arity_counts[arity]);
+ }
+ for (auto &dlogic_count : dlogic_counts)
+ {
+ log(" with %-12s %4d\n", dlogic_count.first.c_str(), dlogic_count.second);
+ }
+ }
+
+ OptLutWorker(dict<IdString, dict<int, IdString>> &dlogic, RTLIL::Module *module, int limit) :
+ dlogic(dlogic), module(module), index(module), sigmap(module)
+ {
+ log("Discovering LUTs.\n");
+ for (auto cell : module->selected_cells())
+ {
+ if (cell->type == "$lut")
+ {
+ int lut_width = cell->getParam("\\WIDTH").as_int();
+ SigSpec lut_input = cell->getPort("\\A");
+ int lut_arity = 0;
+
+ log("Found $lut\\WIDTH=%d cell %s.%s.\n", lut_width, log_id(module), log_id(cell));
+ luts.insert(cell);
+
+ // First, find all dedicated logic we're connected to. This results in an overapproximation
+ // of such connections.
+ pool<RTLIL::Cell*> lut_all_dlogics;
+ for (int i = 0; i < lut_width; i++)
+ {
+ SigBit bit = lut_input[i];
+ for (auto &port : index.query_ports(bit))
+ {
+ if (dlogic.count(port.cell->type))
+ {
+ auto &dlogic_map = dlogic[port.cell->type];
+ if (dlogic_map.count(i))
+ {
+ if (port.port == dlogic_map[i])
+ {
+ lut_all_dlogics.insert(port.cell);
+ }
+ }
+ }
+ }
+ }
+
+ // Second, make sure that the connection to dedicated logic is legal. If it is not legal,
+ // it means one of the two things:
+ // * The connection is spurious. I.e. this is dedicated logic that will be packed
+ // with some other LUT, and it just happens to be connected to this LUT as well.
+ // * The connection is illegal.
+ // In either of these cases, we don't need to concern ourselves with preserving the connection
+ // between this LUT and this dedicated logic cell.
+ pool<RTLIL::Cell*> lut_legal_dlogics;
+ pool<int> lut_dlogic_inputs;
+ for (auto lut_dlogic : lut_all_dlogics)
+ {
+ auto &dlogic_map = dlogic[lut_dlogic->type];
+ bool legal = true;
+ for (auto &dlogic_conn : dlogic_map)
+ {
+ if (lut_width <= dlogic_conn.first)
+ {
+ log(" LUT has illegal connection to %s cell %s.%s.\n", lut_dlogic->type.c_str(), log_id(module), log_id(lut_dlogic));
+ log(" LUT input A[%d] not present.\n", dlogic_conn.first);
+ legal = false;
+ break;
+ }
+ if (sigmap(lut_input[dlogic_conn.first]) != sigmap(lut_dlogic->getPort(dlogic_conn.second)))
+ {
+ log(" LUT has illegal connection to %s cell %s.%s.\n", lut_dlogic->type.c_str(), log_id(module), log_id(lut_dlogic));
+ log(" LUT input A[%d] (wire %s) not connected to %s port %s (wire %s).\n", dlogic_conn.first, log_signal(lut_input[dlogic_conn.first]), lut_dlogic->type.c_str(), dlogic_conn.second.c_str(), log_signal(lut_dlogic->getPort(dlogic_conn.second)));
+ legal = false;
+ break;
+ }
+ }
+
+ if (legal)
+ {
+ log(" LUT has legal connection to %s cell %s.%s.\n", lut_dlogic->type.c_str(), log_id(module), log_id(lut_dlogic));
+ lut_legal_dlogics.insert(lut_dlogic);
+ for (auto &dlogic_conn : dlogic_map)
+ lut_dlogic_inputs.insert(dlogic_conn.first);
+ }
+ }
+
+ // Third, determine LUT arity. An n-wide LUT that has k constant inputs and m inputs shared with dedicated
+ // logic implements an (n-k-m)-ary function.
+ for (int i = 0; i < lut_width; i++)
+ {
+ SigBit bit = lut_input[i];
+ if (bit.wire || lut_dlogic_inputs.count(i))
+ lut_arity++;
+ }
+
+ log(" Cell implements a %d-LUT.\n", lut_arity);
+ luts_arity[cell] = lut_arity;
+ luts_dlogics[cell] = lut_legal_dlogics;
+ luts_dlogic_inputs[cell] = lut_dlogic_inputs;
+ }
+ }
+ show_stats_by_arity();
+
+ log("\n");
+ log("Eliminating LUTs.\n");
+ pool<RTLIL::Cell*> worklist = luts;
+ while (worklist.size())
+ {
+ if (limit == 0)
+ {
+ log("Limit reached.\n");
+ break;
+ }
+
+ auto lut = worklist.pop();
+ SigSpec lut_input = sigmap(lut->getPort("\\A"));
+ pool<int> &lut_dlogic_inputs = luts_dlogic_inputs[lut];
+
+ vector<SigBit> lut_inputs;
+ for (auto &bit : lut_input)
+ {
+ if (bit.wire)
+ lut_inputs.push_back(sigmap(bit));
+ }
+
+ bool const0_match = true;
+ bool const1_match = true;
+ vector<bool> input_matches;
+ for (size_t i = 0; i < lut_inputs.size(); i++)
+ input_matches.push_back(true);
+
+ for (int eval = 0; eval < 1 << lut_inputs.size(); eval++)
+ {
+ dict<SigBit, bool> eval_inputs;
+ for (size_t i = 0; i < lut_inputs.size(); i++)
+ eval_inputs[lut_inputs[i]] = (eval >> i) & 1;
+ bool value = evaluate_lut(lut, eval_inputs);
+ if (value != 0)
+ const0_match = false;
+ if (value != 1)
+ const1_match = false;
+ for (size_t i = 0; i < lut_inputs.size(); i++)
+ {
+ if (value != eval_inputs[lut_inputs[i]])
+ input_matches[i] = false;
+ }
+ }
+
+ int input_match = -1;
+ for (size_t i = 0; i < lut_inputs.size(); i++)
+ if (input_matches[i])
+ input_match = i;
+
+ if (const0_match || const1_match || input_match != -1)
+ {
+ log("Found redundant cell %s.%s.\n", log_id(module), log_id(lut));
+
+ SigBit value;
+ if (const0_match)
+ {
+ log(" Cell evaluates constant 0.\n");
+ value = State::S0;
+ }
+ if (const1_match)
+ {
+ log(" Cell evaluates constant 1.\n");
+ value = State::S1;
+ }
+ if (input_match != -1) {
+ log(" Cell evaluates signal %s.\n", log_signal(lut_inputs[input_match]));
+ value = lut_inputs[input_match];
+ }
+
+ if (lut_dlogic_inputs.size())
+ {
+ log(" Not eliminating cell (connected to dedicated logic).\n");
+ }
+ else
+ {
+ SigSpec lut_output = lut->getPort("\\Y");
+ for (auto &port : index.query_ports(lut_output))
+ {
+ if (port.cell != lut && luts.count(port.cell))
+ worklist.insert(port.cell);
+ }
+
+ module->connect(lut_output, value);
+ sigmap.add(lut_output, value);
+
+ module->remove(lut);
+ luts.erase(lut);
+ luts_arity.erase(lut);
+ luts_dlogics.erase(lut);
+ luts_dlogic_inputs.erase(lut);
+
+ eliminated_count++;
+ if (limit > 0)
+ limit--;
+ }
+ }
+ }
+ show_stats_by_arity();
+
+ log("\n");
+ log("Combining LUTs.\n");
+ worklist = luts;
+ while (worklist.size())
+ {
+ if (limit == 0)
+ {
+ log("Limit reached.\n");
+ break;
+ }
+
+ auto lutA = worklist.pop();
+ SigSpec lutA_input = sigmap(lutA->getPort("\\A"));
+ SigSpec lutA_output = sigmap(lutA->getPort("\\Y")[0]);
+ int lutA_width = lutA->getParam("\\WIDTH").as_int();
+ int lutA_arity = luts_arity[lutA];
+ pool<int> &lutA_dlogic_inputs = luts_dlogic_inputs[lutA];
+
+ auto lutA_output_ports = index.query_ports(lutA->getPort("\\Y"));
+ if (lutA_output_ports.size() != 2)
+ continue;
+
+ for (auto &port : lutA_output_ports)
+ {
+ if (port.cell == lutA)
+ continue;
+
+ if (luts.count(port.cell))
+ {
+ auto lutB = port.cell;
+ SigSpec lutB_input = sigmap(lutB->getPort("\\A"));
+ SigSpec lutB_output = sigmap(lutB->getPort("\\Y")[0]);
+ int lutB_width = lutB->getParam("\\WIDTH").as_int();
+ int lutB_arity = luts_arity[lutB];
+ pool<int> &lutB_dlogic_inputs = luts_dlogic_inputs[lutB];
+
+ log("Found %s.%s (cell A) feeding %s.%s (cell B).\n", log_id(module), log_id(lutA), log_id(module), log_id(lutB));
+
+ if (index.query_is_output(lutA->getPort("\\Y")))
+ {
+ log(" Not combining LUTs (cascade connection feeds module output).\n");
+ continue;
+ }
+
+ pool<SigBit> lutA_inputs;
+ pool<SigBit> lutB_inputs;
+ for (auto &bit : lutA_input)
+ {
+ if (bit.wire)
+ lutA_inputs.insert(sigmap(bit));
+ }
+ for (auto &bit : lutB_input)
+ {
+ if (bit.wire)
+ lutB_inputs.insert(sigmap(bit));
+ }
+
+ pool<SigBit> common_inputs;
+ for (auto &bit : lutA_inputs)
+ {
+ if (lutB_inputs.count(bit))
+ common_inputs.insert(bit);
+ }
+
+ int lutM_arity = lutA_arity + lutB_arity - 1 - common_inputs.size();
+ if (lutA_dlogic_inputs.size())
+ log(" Cell A is a %d-LUT with %zu dedicated connections. ", lutA_arity, lutA_dlogic_inputs.size());
+ else
+ log(" Cell A is a %d-LUT. ", lutA_arity);
+ if (lutB_dlogic_inputs.size())
+ log("Cell B is a %d-LUT with %zu dedicated connections.\n", lutB_arity, lutB_dlogic_inputs.size());
+ else
+ log("Cell B is a %d-LUT.\n", lutB_arity);
+ log(" Cells share %zu input(s) and can be merged into one %d-LUT.\n", common_inputs.size(), lutM_arity);
+
+ const int COMBINE_A = 1, COMBINE_B = 2, COMBINE_EITHER = COMBINE_A | COMBINE_B;
+ int combine_mask = 0;
+ if (lutM_arity > lutA_width)
+ {
+ log(" Not combining LUTs into cell A (combined LUT wider than cell A).\n");
+ }
+ else if (lutB_dlogic_inputs.size() > 0)
+ {
+ log(" Not combining LUTs into cell A (cell B is connected to dedicated logic).\n");
+ }
+ else if (lutB->get_bool_attribute("\\lut_keep"))
+ {
+ log(" Not combining LUTs into cell A (cell B has attribute \\lut_keep).\n");
+ }
+ else
+ {
+ combine_mask |= COMBINE_A;
+ }
+ if (lutM_arity > lutB_width)
+ {
+ log(" Not combining LUTs into cell B (combined LUT wider than cell B).\n");
+ }
+ else if (lutA_dlogic_inputs.size() > 0)
+ {
+ log(" Not combining LUTs into cell B (cell A is connected to dedicated logic).\n");
+ }
+ else if (lutA->get_bool_attribute("\\lut_keep"))
+ {
+ log(" Not combining LUTs into cell B (cell A has attribute \\lut_keep).\n");
+ }
+ else
+ {
+ combine_mask |= COMBINE_B;
+ }
+
+ int combine = combine_mask;
+ if (combine == COMBINE_EITHER)
+ {
+ log(" Can combine into either cell.\n");
+ if (lutA_arity == 1)
+ {
+ log(" Cell A is a buffer or inverter, combining into cell B.\n");
+ combine = COMBINE_B;
+ }
+ else if (lutB_arity == 1)
+ {
+ log(" Cell B is a buffer or inverter, combining into cell A.\n");
+ combine = COMBINE_A;
+ }
+ else
+ {
+ log(" Arbitrarily combining into cell A.\n");
+ combine = COMBINE_A;
+ }
+ }
+
+ RTLIL::Cell *lutM, *lutR;
+ pool<SigBit> lutM_inputs, lutR_inputs;
+ pool<int> lutM_dlogic_inputs;
+ if (combine == COMBINE_A)
+ {
+ log(" Combining LUTs into cell A.\n");
+ lutM = lutA;
+ lutM_inputs = lutA_inputs;
+ lutM_dlogic_inputs = lutA_dlogic_inputs;
+ lutR = lutB;
+ lutR_inputs = lutB_inputs;
+ }
+ else if (combine == COMBINE_B)
+ {
+ log(" Combining LUTs into cell B.\n");
+ lutM = lutB;
+ lutM_inputs = lutB_inputs;
+ lutM_dlogic_inputs = lutB_dlogic_inputs;
+ lutR = lutA;
+ lutR_inputs = lutA_inputs;
+ }
+ else
+ {
+ log(" Cannot combine LUTs.\n");
+ continue;
+ }
+
+ pool<SigBit> lutR_unique;
+ for (auto &bit : lutR_inputs)
+ {
+ if (!common_inputs.count(bit) && bit != lutA_output)
+ lutR_unique.insert(bit);
+ }
+
+ int lutM_width = lutM->getParam("\\WIDTH").as_int();
+ SigSpec lutM_input = sigmap(lutM->getPort("\\A"));
+ std::vector<SigBit> lutM_new_inputs;
+ for (int i = 0; i < lutM_width; i++)
+ {
+ bool input_unused = false;
+ if (sigmap(lutM_input[i]) == lutA_output)
+ input_unused = true;
+ if (!lutM_input[i].wire && !lutM_dlogic_inputs.count(i))
+ input_unused = true;
+
+ if (input_unused && lutR_unique.size())
+ {
+ SigBit new_input = lutR_unique.pop();
+ log(" Connecting input %d as %s.\n", i, log_signal(new_input));
+ lutM_new_inputs.push_back(new_input);
+ }
+ else if (sigmap(lutM_input[i]) == lutA_output)
+ {
+ log(" Disconnecting cascade input %d.\n", i);
+ lutM_new_inputs.push_back(SigBit());
+ }
+ else
+ {
+ log(" Leaving input %d as %s.\n", i, log_signal(lutM_input[i]));
+ lutM_new_inputs.push_back(lutM_input[i]);
+ }
+ }
+ log_assert(lutR_unique.size() == 0);
+
+ RTLIL::Const lutM_new_table(State::Sx, 1 << lutM_width);
+ for (int eval = 0; eval < 1 << lutM_width; eval++)
+ {
+ dict<SigBit, bool> eval_inputs;
+ for (size_t i = 0; i < lutM_new_inputs.size(); i++)
+ {
+ eval_inputs[lutM_new_inputs[i]] = (eval >> i) & 1;
+ }
+ eval_inputs[lutA_output] = evaluate_lut(lutA, eval_inputs);
+ lutM_new_table[eval] = (RTLIL::State) evaluate_lut(lutB, eval_inputs);
+ }
+
+ log(" Cell A truth table: %s.\n", lutA->getParam("\\LUT").as_string().c_str());
+ log(" Cell B truth table: %s.\n", lutB->getParam("\\LUT").as_string().c_str());
+ log(" Merged truth table: %s.\n", lutM_new_table.as_string().c_str());
+
+ lutM->setParam("\\LUT", lutM_new_table);
+ lutM->setPort("\\A", lutM_new_inputs);
+ lutM->setPort("\\Y", lutB_output);
+
+ luts_arity[lutM] = lutM_arity;
+ luts.erase(lutR);
+ luts_arity.erase(lutR);
+ lutR->module->remove(lutR);
+
+ worklist.insert(lutM);
+ worklist.erase(lutR);
+
+ combined_count++;
+ if (limit > 0)
+ limit--;
+ }
+ }
+ }
+ show_stats_by_arity();
+ }
+};
+
+static void split(std::vector<std::string> &tokens, const std::string &text, char sep)
+{
+ size_t start = 0, end = 0;
+ while ((end = text.find(sep, start)) != std::string::npos) {
+ tokens.push_back(text.substr(start, end - start));
+ start = end + 1;
+ }
+ tokens.push_back(text.substr(start));
+}
+
+struct OptLutPass : public Pass {
+ OptLutPass() : Pass("opt_lut", "optimize LUT cells") { }
+ void help() YS_OVERRIDE
+ {
+ // |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
+ log("\n");
+ log(" opt_lut [options] [selection]\n");
+ log("\n");
+ log("This pass combines cascaded $lut cells with unused inputs.\n");
+ log("\n");
+ log(" -dlogic <type>:<cell-port>=<LUT-input>[:<cell-port>=<LUT-input>...]\n");
+ log(" preserve connections to dedicated logic cell <type> that has ports\n");
+ log(" <cell-port> connected to LUT inputs <LUT-input>. this includes\n");
+ log(" the case where both LUT and dedicated logic input are connected to\n");
+ log(" the same constant.\n");
+ log("\n");
+ log(" -limit N\n");
+ log(" only perform the first N combines, then stop. useful for debugging.\n");
+ log("\n");
+ }
+ void execute(std::vector<std::string> args, RTLIL::Design *design) YS_OVERRIDE
+ {
+ log_header(design, "Executing OPT_LUT pass (optimize LUTs).\n");
+
+ dict<IdString, dict<int, IdString>> dlogic;
+ int limit = -1;
+
+ size_t argidx;
+ for (argidx = 1; argidx < args.size(); argidx++)
+ {
+ if (args[argidx] == "-dlogic" && argidx+1 < args.size())
+ {
+ std::vector<std::string> tokens;
+ split(tokens, args[++argidx], ':');
+ if (tokens.size() < 2)
+ log_cmd_error("The -dlogic option requires at least one connection.\n");
+ IdString type = "\\" + tokens[0];
+ for (auto it = tokens.begin() + 1; it != tokens.end(); ++it) {
+ std::vector<std::string> conn_tokens;
+ split(conn_tokens, *it, '=');
+ if (conn_tokens.size() != 2)
+ log_cmd_error("Invalid format of -dlogic signal mapping.\n");
+ IdString logic_port = "\\" + conn_tokens[0];
+ int lut_input = atoi(conn_tokens[1].c_str());
+ dlogic[type][lut_input] = logic_port;
+ }
+ continue;
+ }
+ if (args[argidx] == "-limit" && argidx + 1 < args.size())
+ {
+ limit = atoi(args[++argidx].c_str());
+ continue;
+ }
+ break;
+ }
+ extra_args(args, argidx, design);
+
+ int eliminated_count = 0, combined_count = 0;
+ for (auto module : design->selected_modules())
+ {
+ OptLutWorker worker(dlogic, module, limit - eliminated_count - combined_count);
+ eliminated_count += worker.eliminated_count;
+ combined_count += worker.combined_count;
+ }
+ if (eliminated_count)
+ design->scratchpad_set_bool("opt.did_something", true);
+ if (combined_count)
+ design->scratchpad_set_bool("opt.did_something", true);
+ log("\n");
+ log("Eliminated %d LUTs.\n", eliminated_count);
+ log("Combined %d LUTs.\n", combined_count);
+ }
+} OptLutPass;
+
+PRIVATE_NAMESPACE_END
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